The invention relates to a multimode interference coupler (MMI) having at least one supply waveguide and at least one output waveguide.
MMIs of the type mentioned at the outset comprise a waveguide in which a plurality of optical modes can be excited. At least one supply waveguide, usually a single-mode supply waveguide, supplies this waveguide with optical signals which excite the modes which are able to propagate in the MMI. If a plurality of the modes which are able to propagate are excited, they come to interfere inside the MMI. At least one maximum of the interference pattern is injected into an output waveguide, usually a single-mode output waveguide.
MMIs are used, in particular, in optical data transmission networks to divide optical signals from one supply waveguide, for example, among two or more output waveguides. For this purpose, the geometry and refractive index of the MMI are configured in such a manner that the desired field strength and phase angle of the output signals produced are achieved.